Linux: Use After Free
CVE-2022-48950 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 8bffa95ac19ff27c8261904f89d36c7fcf215d59, 78e1317a174edbfd1182599bf76c092a2877672c, 517e6a301f34613bff24a8e35b5455884f2d83d8 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.25% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 8bffa95ac19ff27c8261904f89d36c7fcf215d59 or 78e1317a174edbfd1182599bf76c092a2877672c or 517e6a301f34613bff24a8e35b5455884f2d83d8 or 5.15.84, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.84 or 6.0.14, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | ca7b0a10287e2733bdafb01ef0d4038536625fe3 up to, but not including, 8bffa95ac19ff27c8261904f89d36c7fcf215d59; 078c12ccf1fb943cc18c84894c76113dc89e5975 up to, but not including, 78e1317a174edbfd1182599bf76c092a2877672c; ca6c21327c6af02b7eec31ce4b9a740a18c6c13f up to, but not including, 517e6a301f34613bff24a8e35b5455884f2d83d8; 5.15.77 up to, but not including, 5.15.84; 6.0.7 up to, but not including, 6.0.14 | 8bffa95ac19ff27c8261904f89d36c7fcf215d59, 78e1317a174edbfd1182599bf76c092a2877672c, 517e6a301f34613bff24a8e35b5455884f2d83d8, 5.15.84, 6.0.14 |
| Linux | Linux Kernel | before 5.15.84; 5.16 up to, but not including, 6.0.14; 6.1 | 5.15.84, 6.0.14 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: perf: Fix perf_pending_task() UaF Per syzbot it is possible for perf_pending_task() to run after the event is free()'d. There are two related but distinct cases: - the task_work was already queued before destroying the event; - destroying the event itself queues the task_work. The first cannot be solved using task_work_cancel() since perf_release() itself might be called from a task_work (____fput), which means the current->task_works list is already empty and task_work_cancel() won't be able to find the perf_pending_task() entry. The simplest alternative is extending the perf_event lifetime to cover the task_work. The second is just silly, queueing a task_work while you know the event is going away makes no sense and is easily avoided by re-arranging how the event is marked STATE_DEAD and ensuring it goes through STATE_OFF on the way down.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Use After Free vulnerabilities
- 7.0 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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